JP3105273B2 - Inspection method of resist pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a resist pattern when manufacturing a high-density integrated circuit such as an LSI and a super LSI.

[0002]

2. Description of the Related Art In recent years, the performance of semiconductor integrated circuits and the like has been improved.
The demand for higher integration is on the rise, and electron beams, instead of conventional photolithography using ultraviolet light,
Efforts have been made to establish an ultrafine pattern processing technique by lithography using soft X-rays, ion beams, and the like. In particular, in the manufacture of photomasks, electron beam lithography has already been industrially put to practical use, and direct writing of electron beams on wafer substrates has been attempted. On the other hand, in order to enable such ultra-fine lithography technology, the requirements for drawing accuracy of an exposure apparatus have become strict, and the resist material used must have properties that can meet the demands. Is considered important. In addition, many resists have been developed, but in general, a positive type, in which a collapse reaction is caused by irradiation with an electron beam and the irradiated part is solubilized, and a cross-linking reaction is caused by irradiation with an electron beam and the irradiated part is generally formed. It is classified as a negative type that insolubilizes. A positive resist is superior to a negative resist in that an ultrafine high resolution can be formed.

In a manufacturing process of a semiconductor integrated circuit or the like, a resist pattern formed on a substrate is inspected for the purpose of quality control and the like. When the resist pattern is fine, a scanning electron microscope is used. (SEM).

[0004]

However, when a resist is formed on a substrate by electron beam, ion beam or X-ray, a resist pattern is formed in a complicated or fine pattern already formed on the substrate. In this case, when the resist pattern is observed with a SEM, a clear image of the resist pattern cannot be obtained. Conventionally, only a low-precision inspection is performed from an unclear resist pattern image. there were.

[0005] Inspection of the dimensions of a resist pattern has been carried out by breaking a substrate and observing a cross section thereof with an SEM. As described above, various methods for observing a resist pattern using an SEM have been proposed. However, it is very difficult to observe the resist pattern in real time and with high accuracy in any method. Was.

The present invention has been made in view of the foregoing circumstances, and has been made in consideration of the above-described circumstances. Inspection of a resist pattern capable of easily observing the resist pattern without affecting the properties of the substrate involved in the manufacturing process and without breaking the substrate. It is intended to provide a method.

[0007]

As a result of various studies for achieving the above object, fine or complicated patterns are formed in a resist pattern forming process using an electron beam, a focused ion beam, ultraviolet rays or X-rays on a substrate. After forming the resist pattern in, without directly inspecting the resist pattern, by forming an inspection pattern simultaneously with the resist pattern in a predetermined location of the substrate, by inspecting the inspection pattern, The present invention has been completed by finding that the above problem can be solved by evaluating the resist pattern. Therefore, the method for inspecting a resist pattern according to the present invention includes a step of forming the resist pattern in a fine or complicated pattern in a resist pattern forming step using an electron beam, a focused ion beam, ultraviolet rays or X-rays on a substrate. Inspection of a resist pattern that enables the evaluation of the resist pattern by forming an inspection pattern simultaneously with the resist pattern on a portion of the substrate where fine or complicated processing is not performed, and inspecting the inspection pattern. A method, wherein a lower resist film and an upper resist film are formed on the resist pattern, a resist pattern having a predetermined width is formed on the upper resist film, and a lower resist film in the resist pattern formed on the upper resist film is formed. The resist film has a resist pattern formed on the upper resist film. A resist pattern having a predetermined width smaller than the predetermined width is formed, a lower resist film and an upper resist film are formed on the inspection pattern, and the upper resist film is formed on the upper resist film of the resist pattern. A resist pattern having a predetermined width wider than the formed resist pattern is formed, and the lower resist film in the resist pattern formed on the upper resist film has a smaller width than the resist pattern formed on the upper resist film. A resist pattern having a predetermined width is formed, and the length of the resist pattern formed on the lower resist film of the inspection resist pattern is measured, whereby the resist pattern formed on the lower resist film of the resist pattern is measured. Is characterized by evaluating the dimensions of

[0008]

In general, the length measurement inspection of a resist pattern becomes a problem when the resist pattern exists in a fine or complicated pattern. At this time, in order to measure the length of the resist pattern without breaking the substrate, the resist pattern is formed at a predetermined location on the same substrate that has no processing such as steps and does not affect the present pattern when the resist pattern is formed. A pattern may be formed, and the inspection pattern may be inspected to evaluate the resist pattern of the present pattern. In other words, the correspondence between the dimensions of the main pattern and the inspection pattern is checked in advance, and the dimensions of the main pattern are known by actually measuring the length of the inspection pattern that can be measured by SEM after forming the resist. The inspection of the resist pattern of this main pattern can be performed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, an HEMT (High Electron Mobility Transistor) using a GaAs wafer substrate will be described below.
An example in which a mushroom type gate of a ron Mobility Transistor device is manufactured will be described.

FIG. 1 is a sectional view showing the steps of a method for forming a resist pattern, and FIG. 2 is a sectional view showing the steps of a method for forming an inspection pattern for measuring a line width. FIG.
1 is a semi-insulating GaAs substrate, 2 is a high-purity GaAs epitaxial layer, 3 is a two-dimensional electron channel, and 4 is an n-type AlGaAs.
5, a source electrode, 6 a drain electrode, 7 a lower resist film, 8 an upper resist film, 9, 10 an electron beam, 11
Denotes a mushroom type gate forming pattern, 12 denotes a gate electrode metal film, and 13 denotes a mushroom type gate.

First, as shown in FIG. 1A, a high-purity GaAs epitaxial layer 2 is formed on a semi-insulating GaAs substrate 1, and a two-dimensional electron channel 3 is formed on the surface of the high-purity GaAs epitaxial layer 2. An n-type AlGaAs layer 4 is formed, and further, for example, an alloy of Au and Ge or Au alone is vacuum-deposited thereon to form source and drain electrodes 5 and 6, and a two-dimensional electron channel 3 is formed. Alloying was performed to obtain ohmic contact.

Next, as shown in FIG. 1B, a low-sensitivity resist containing polymethyl methacrylate as a main component (trade name:
OHBR-1000 manufactured by Tokyo Ohka Co., Ltd.)
Pre-baking was performed at 170 ° C. for 30 minutes to obtain a lower resist film 7 having a thickness of 0.2 μm. Then, a high-sensitivity resist (trade name, Sanyo SEBR-115) containing polymethyl methacrylate as a main component was spin-coated. Things at 170 ℃ 3
Prebaking was performed for 0 minutes to obtain an upper resist film 8 having a thickness of 0.6 μm.

Next, as shown in FIG. 1C, an electron beam 9 for a thick pattern having a width of 0.7 μm is irradiated with an acceleration voltage of 20 kV and an exposure amount of 2 kV.
Irradiation was performed at μC / cm ² to draw a predetermined pattern. At the same time, as shown in FIG. 2A, an electron beam drawing 14 having a width of 5 μm was previously performed on a portion where a pattern for inspection is to be formed. In the above electron beam writing, the exposure amount is small, and the sensitivity of the lower resist film 7 is low.
The width pattern is drawn only on the upper resist film 8.

When the above-described drawing is completed, the developing solution (methyl isobutyl ketone: isopropyl alcohol =
1: 3), immersed in a rinse solution (isopropyl alcohol) at 23 ° C. for 30 seconds, rinsed at 23 ° C. for 60 seconds, and rinsed to form an upper resist pattern width of 0.7 μm as shown in FIG. 1D. did.

Next, as shown in FIG. 1D, an electron beam 10 for a narrow hole pattern having a width of 0.25 μm is applied with an acceleration voltage of 20 kV.
V, irradiation was performed at an exposure amount of 100 μC / cm ² , and a predetermined pattern was drawn. As a result, the lower resist film 7 has a thickness of 0.25 μm.
A thin pattern of m width is drawn. At the same time, FIG.
As shown in the figure, an electron beam drawing 15 for a narrow hole pattern having a width of 0.25 μm was performed in a pattern having a width of 5 μm.

When the lower resist portion of the pattern 11 for forming a mushroom type gate shown in FIG. 1E formed as described above is observed from the upper surface with a SEM to measure the size of the lower resist portion, the size of the opening of the upper resist is small. And the clear image of the lower resist cannot be obtained. Therefore, the inspection resist pattern 16 shown in FIG.
Is observed by SEM, and the length is measured. As a result, the pattern 1 for forming a mushroom type gate, which was checked in advance,
1 lower layer resist part dimensions and inspection resist pattern 1
The dimension of the lower resist portion of the pattern 11 for forming a mushroom type gate can be confirmed from the relationship with the dimension of 6.

Using the thus obtained mushroom-type gate forming pattern 11 as a mask, Al is deposited by vapor deposition to form a gate electrode metal film 12 as shown in FIG. 1F, and then acetone is used. Upper resist film 8
And the lower resist film 7 is dissolved and removed, and as shown in FIG. 1G, the gate length is 0.25 μm, the upper width is 0.7 μm, and the length is 200 μm.
Au mushroom type gate 13 was formed.

[0018]

As is apparent from the above description, according to the present invention, it is possible to inspect a resist pattern for a mushroom type gate with high accuracy without adding a new processing step.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing steps of a method for forming a resist pattern according to the present invention.

FIG. 2 is a cross-sectional view showing the steps of a method of forming an inspection pattern for measuring a line width.

[Explanation of symbols]

DESCRIPTION OF REFERENCE NUMERALS 1: semi-insulating GaAs substrate, 2: high-purity GaAs epitaxial layer, 3: two-dimensional electron channel, 4: n-type AlGaAs layer, 5
... source electrode, 6 ... drain electrode, 7 ... lower layer resist film, 8 ... upper layer resist film, 9, 10 ... electron beam, 11 ... pattern for forming a mushroom type gate, 12 ... gate electrode metal film, 13 ... mushroom type gate.

Claims (1)

(57) [Claims] An electron beam, a focused ion beam,
In a resist pattern forming step using ultraviolet rays or X-rays, after forming the resist pattern in a fine or complicated pattern, an inspection pattern is formed on the portion of the substrate where fine or complicated processing is not performed with the resist pattern. A method of inspecting a resist pattern, comprising: simultaneously forming and inspecting the inspection pattern, whereby the resist pattern can be evaluated, wherein a lower resist film and an upper resist film are formed on the resist pattern; A resist pattern having a predetermined width is formed on the film, and a lower resist film in the resist pattern formed on the upper resist film has a predetermined width smaller than the resist pattern formed on the upper resist film. A resist pattern is formed. A resist film having a predetermined width wider than the resist pattern formed on the upper resist film of the resist pattern is formed on the upper resist film, and the upper resist film is formed on the upper resist film. In the lower resist film in the formed resist pattern, a resist pattern having a predetermined width narrower than the resist pattern formed in the upper resist film is formed, and is formed in the lower resist film of the inspection resist pattern. A method for inspecting a resist pattern, comprising: measuring a dimension of a resist pattern described above to evaluate a dimension of a resist pattern formed on a lower resist film of the resist pattern.